Clamp attachment



Jan. 29, 1963 o. E. BIHR 3,075,663

CLAMP ATTACHMENT Filed May 27. 1960 4 Sheets-Sheet 1 FIG. I

INVENTOR.

OTTO E. BIHR ATTORNEY Jan. 29, 1963 0. E. BIHR CLAMP ATTACHMENT 4Sheets' 2 Filed y 27. 1960 mu I fisilmil i Q\ I I I I I I LV/V/ mm 9.6gm g INVENTOR.

O E. BIHR BY f/MWJM ATTORNEY Jan. 29, 1963 Filed May 2'7. 1960 O. E.BlHR CLAMP ATTACHMENT FlG. 5

I IIIIIIIII! 4 Sheets-Sheet 3 INVENTOR.

OTTO E. BIHR BY /wm ATTORNEY Jan. 29, 1963 o. E. BlHR 3, ,6 3

CLAMP ATTACHMENT Filed May 27. 1960 4 Sheets-Sheet 4 INVEN TOR.

OTTO E. BIHR ATTORN EY Patented Jan. 29, 1963 3,ti75,6t53 CLAMPATTACHMENT Gtto E. Bihr, Essen-Altenessen, Germany, assignor to RuhrIntrans Huhstapier, Gnnba a German com- P 3 Filed May 27, 196i), er. N32,416

Ciaims priority, application Germany June 3, 1959 7 Claims. (Cl. 214655)This invention relates to an attachment for industrial trucks, and moreparticularly to improvements in a clamping attachment for lift truckswhich is especially suited for handling stacks of building blocks,bricks, and the like wherein at least two laterally spaced fork arms areprovided having facing sides equipped with clamping members for engagingand holding material to be conveyed.

Heretofore, it has been generally known to provide facing clamp membersin fork arms of the type contemplated in which the clamp members areresponsive to hydraulic or pneumatic fluid pressure supplied by a mainpressure generating system, including a pump or compressor, whi h isconnected to the engine of the lift truck.

It is an important object of the present invention to provide agenerally improved clamping mechanism of the type under consideration.This is achieved in large part by connecting clamping members with aclosed pressure system which may be filled with a hydraulic or pneumaticpressure-transmission medium in which pressure responsive members, suchas pistons, are actuated by the mass of material to be conveyed toprovide fluid pressure at the facing clamping members located in thesides of fork arms. When the material conveyed is deposited the pressuremembers automatically release the clamping members. The device of thepresent invention is, therefore, capable of engaging, conveying and depositing material without dependency upon any independ ent pressuregenerating means, such as a pump or air compressor. An additionalresulting advantage in the use of a hydraulic pressure-transmissionmedium, for example, is that hydraulic lines between the fork arms,which is preferably movable vertically in a lifting mast of a lifttruck, and a stationary pump are eliminated.

Thus, the attachment unit becomes a less cumbersome and neater package,and by omission of the usual movable connecting hydraulic lines the unitis less subject to malfunctioning in operation and, importantly, isinsensitive to fluid losses resulting from leakage in the independentsystem.

If desired, the pressure transmitting system between the pressureproducing pistons and the pressure responsive clamping members may befilled with a mechanical pressure transmission medium as, for example,steel balls, which is of particular advantage in applications whichrequire that the pressure transmission medium be insensitive to largevariations in temperature. The use of steel balls in the aforesaidmanner as an alternative to the use of fluid, hydraulic or otherwise,makes possible the use of the attachment in areas of widely varyingtemperature. Also, of course, no leakage losses are encountered in theuse of a mechanical pressure trans mission medium.

The fork arms are preferably equipped with pressure limiters to limitthe maximum clamping pressure which can be applied to the materialconveyed, thereby pro tecting same against possible damage. Also,adjustable pressure reservoirs in the system are provided so that theoperating pressure of the pressure transmission mediumcan be varied asdesired depending upon requirements of different operating conditions.

Another object of the invention is therefore to provide a closed circuitpressure transmission system in a clamping attachment of the typecontemplated wherein means are provided to apply clamping pressure as afunction of the load to be conveyed and to release such clampingpressure upon deposite of the load.

Other objects and advantages of the present invention will appear as thedescription proceeds.

Now, in order to acquaint those skilled in the art with the manner ofconstructing and using clamping means, in accordance with the principlesof my present invention, I shall describe in connection with theaccompanying drawings, preferred embodiments of the invention.

In the drawings:

FIGURE 1 is a side view primarily in elevation which illustrates theclamping attachment suspended on the lifting mast of an industrialtruck;

FIGURE 2 is a plan view of FIGURE 1;

FIGURE 3 is an enlarged vertical longitudinal section through a fork armalong the line 3-3 in FIGURE 2;

FIGURE 4 is an enlarged vertical longitudinal section through a fork armalong the line 44- in FIGURE 2;

FIGURE 5 is an enlarged vertical section through a pressure reservoirshown in section in FIGURE 1;

FIGURE 6 is a vertical section similar to FIGURE 3 but illustrating amodified form of the invention;

FIGURE 7 is a vertical section similar to FIGURE 4 but illustratinganother portion of the modified form of the invention shown in FIGURE 6;

FIGURE 8 is a schematic representation of the form of the inventionshown in FIGURES 3 and 4; and

FIGURE 9 is a schematic representation of the modified form of theinvention shown in FIGURES 6 and 7.

Referring now in detail to the drawings, a lifting mast assembly 1 issupported in well-known manner upon the forward end of an industrialtruck 2 and supports in turn for vertical movement therein a liftbracket 3 to which is connected a transverse support plate 4. Hydraulichoist motor means la is associated with the lifting mast 1 and isconnected by known sprocket and chain means with a transverse plate 4for actuating same vertically in lifting mast 1 in a well-known manner.

A conveyor fork arm assembly 5 is supported from the plate 4 by a pairof vertically extending shanks 11. Assembly 5 includes a plurality offork arms 6, five fork arms being shown, which are mounted intransversely spaced and parallel relation to each other to providelongitudinally extending openings in which material to be engaged can belocated. The facing sides of the fork arms are equipped with clampingmembers 7 which are adapted to secure the material to be conveyed, aswill be described below.

Clamping members '7 are spaced equally apart over the length of eachfork arm, and are connected by common pressure conduit means 8 of aclosed pressure system which may be filled, for example, with eitherhydraulic or pneumatic fluid or with a mechanical pressure transmissionmeans such as steel balls. The closed pressure system is equipped withpiston members 9 Which are connected to a carrier plate 10 overlyingeach fork arm 6 and parallel to it. Carrier plates 10 preferably extendover the entire length of the respective fork arms 6, as show in FIGURES1 and 2.

In each of two vertical shanks 11 which are connected to the forkconveyor assembly 5 and which support the latter from transverse plate4, there is provided a pressure reservoir (FIG. 5) comprising a springoperated plunger 12 having a sealing ring 13 associated therewith, andan adjusting nut 14 providing pre-load pressure on the plunger through aspring 15. The system, hydraulic as shown, is filled by removing nut 14and plunger 12 and then filling the pressure system 8 with a hydraulicfluid. In frigid areas glycerin may be used as a pressure transmissionmedium to withstand relatively extreme degrees of cold; If'theattachment is to be equipped with a pneumatic medium it is expedient toprovide in the area of hollow space 16 below the plunger 12 a connector,not shown, for receiving compressed air or the like.

As illustrated in FIGURE 3, the clamping members 7 are located incylindrical'spaces '17' which are connected with the pressure system 8.Each of the clamp members is equipped at its outer end with a clamp jaw18 which preferably has a serrated surface 19. An annular'packing 20 islocated at the inner end of each clamp member 7. A collar 21 of eachclamp member abuts one end of a return spring 22 which is, providedbetween the inside wall ofspace 17 and .the clamptmember' 7. Each spring22 at its opposite end is supported by a nut 24 which is threaded intoeach fork arm 6 flush with the latters outer surface 23.

In FIGURE 4 is shown the relationship of one of pressure pistons 9,which is secured to carrier plate 10 as bywelding, to the system. 8.Piston 9 is, located in a cylindrical space 25 which is connected withpressure system 8, and at the upper end of piston 9 is attached thecarrier plate 10. A circular packing 26 surrounds the lower end ofpiston 9. A compression spring 27 is located between each carrier plateand its fork arm 6 which serves as a return spring in a manner to bedescribed. Preferably a stop member 28 islocated on each forkarm toprovide a pressure limiting means for the respective piston 9,. Thestops may, of course, be ad'- justable within the fork arm to providefor variations in the length of stroke of pistons 9.

Referring now especially to FIGURE 8, the operation .of the aboveembodiment will be described. The material to be conveyed as, forexample, t-ile s,;br;icks or blocks 29, is arranged in a well-knownmanner so that the, fork assembly with its fork arms 6 can be driven inthe direction indicated by arrow a (FIG, 1) into hollow spaces 30, whichare located-between rows formed in the bottom layer of such material sothat thefork arms may assume the position shown in FIGURE 2' withrespect to the lowermost row-of the stack of material. The adjacent -orsecond layer and succeeding layers of such material 29 are stackedsolidly upon the lower rows thereof without providing spaces such' asindicated at numeral'30, whereby the location of fork assembly 5 asshown. in FIGURE 2 causes carrier plates to be situated directly beneaththe second layer .or the stack of bricks or other material, as shown in.FIGURE 1.

As. hoist motor 1a is energized to. raise the unit in lifting mast 1carrier plates 10 first come to bear on the undersides of the secondlayer of material and, because of the weight of the material, they arecaused to move relative to fork arms 6 in the direction indicated byarrow b which causes pistons 9 to apply pressureto the fluid in system8, thereby transmitting clamping pressure against piston surface 31' ofcollar 21 of the clamping member 7 so that the clamping members arepressed against the material in a direction indicated by arrow 0. Inorder to adjust the clampingpressure to the nature of the bricks orother material and to preclude damage to the clamping members ormateria'l by excessive pressures, adjusting nuts 14 of the reservoir 11may be adjusted, and pressure limiters 28 also adjusted,;if;necessary,to limit the available stroke of pistons 9.

Thus, the clamping of the material by member 7 is accomplishedadvantageously prior to lifting of the material by the fork assembly 5.This is in contrast to prior known structures for a similar purposewherein pumps and the like have been providedfor the purpose ofsupplying pressure fluid to' clamp members which engage the bricks orother material. It will be apparent that the present invention insuresthat'the material is not lifted until sufficient clamping pressure isprovided to insure secure gripping thereof. This avoids 'both apos-.1sible loss 0f the; load and any relative movement between the clampmember ends 18 and the load which would lead to undue wear of the clampmembers and to undesirable abrasion of the bricks or other material. Ofcourse, other forms of the clamping members 7 can be provided than thatshown. For example, instead of using jaws 18 .it may be found desirableto utilize a hardened steel ball secured to clamp member 7 and usablewith extremely hard bricks, for example, so that the surface thereofwill not be damaged by the serration of the clamping aws.

When the material conveyed is to be deposited, pistons 9 are restored toinitial position by springs 27, the fork arm 6 having been lowered sothat the lowest row of bricks rests on the ground and carrier plates 10are lowered out of contact with the second layer of bricks. The pressureof the medium in system 8 is thereby released and clamp members 7 arethereupon restored to initial position by return springs 22. Returnsprings 22 can be omitted in many instances inasmuch as a vacuum tendsto'be developed within system 8 coincident with upward movement ofpistons 9 relative to fork arms 6 in the direction indicated by arrow d,which allows clamp member 7 to return in, the direction of arrow e tothe starting position thereof; Thus, the clamp jaws are actuatedawayfrom the bricks and the fork assembly can then be moved by the lifttruck in the direction indicated by arrow 1 (FIGURE 1) out of the brick,stack.

A second embodiment of the invention is illustrated in FIGURES 6, 7 and9, wherein an annular chamber 33 is located between each collar 21 andclamp jaw 18 in fork arm, 6 and communicates with a passage 34 which isfilled with the pressure transmission medium. Passage 34 connects eachannular chamber 33 with a chamber 35 formed between a piston rod 36 of areturn piston 37 and the inner wall of a cylindrical space 38. Pistonrod 36 is joined with carrier plate 10 as by welding. Each return piston37 is provided with a circularpacking member 39 and is sealed withrespect to fork arm 6 by packing means 40 and 41 which are located inposition by a nut 42. A vent 44 to atmosphere is provided in the spacebeneath piston 37. The annular chamber 33 is sealed by a fiat sealingmember 45 which is held in position by a nut 47 furnished with a ringpacking 46.

Clamping of the bricks or other material is accomp lished in essentiallythe same manner as described earlier in respect of FIGURES 3, 4 and 8.The; return movement of each clamp member 7 to starting position forreleasing each fork arm 6 from the stack of material after depositingsame takes place in the independent upward movement of each piston 9which is raised byspring 27, such spring action simultaneously causingupward movement of return pistons 37 which releases the pressure inconduit 34 permitting inward movement of clamping member 7. In orderalways to be-able to adjust'the manner of operation of the return piston37 to the manner of operation of the fork assembly, apressure reservoir48 is provided, schematically illustrated in FIGURE 9, which is designedin the same manner as reservoir 11.

Now, while I have shown and described only two embodiments of thepresent invention, it will be understood that various rearrangements andmodifications may be made therein without departing from the spirittandscope of my invention.

I claim:

1. A device usable with lift trucks andthe like for-engaging,transporting and depositing material such as bricks, tile, blocks or thelike, comprising a pair of fork arms supported from the truck andextending forwardly thereof in parallel spaced relation, a plurality ofpairs of opposed reciprocable clamping members mounted inside the forkarms and extending outwardly thereof into the space formed therebetween,'a common fluid pressure transmitting medium interconnecting all of'saidclamping membersin each fork arm, and'a'fiuidpresusre producing meansmounted inside the fork arms for generating fluid e, ovaees pressure inthe pressure transmitting medium upon lifting movement of the fork armsto support a load, said fluid pressure producing means being the solemeans associated with the device for generating fluid pressure in saidpressure transmission medium, said generated fluid pressure transmittingthrough said common fluid pressure transmitting medium forces causingall of said clamping members in each fork arm to be actuated toward eachother into the space between the fork arms.

2. A device for handling material such as bricks, tile, blocks or thelike, comprising a pair of longitudinally extending and transverselyspaced parallel arm members, movable clamping means extending inwardlyinto the space between the arm members in opposed facing relation, aplurality of fluid pressure producing means associated with each armmember operatively connected to the clamping means, said operativeconnection including a common fluid conduit means conducting a fluidpressure transmitting medium between the clamping means and theplurality of pressure producing means in each arm member, said fluidpressure producing means being activated upon lifting movement of thearm members to forcefully engage a load to pressurize the medium in thecommon fluid conduit whereby to simultaneously actuate the opposedclamping means in opposite directious into the space between the armmembers, a fluid reservoir connected to the fluid conduit means, andmeans in said reservoir for producing an initial pressure level in thepressure transmitting medium.

3. A device as claimed in claim 2 wherein other fluid means areassociated with the clamping means and with the pressure producing meansfor actuating same to an initial non-clamping position upon movement ofthe arm members downwardly to disengage the load.

4. A clamping fork arm assembly usable with industrial trucks and thelike for engaging, transporting and depositing material such as bricks,tile, blocks or the like, comprising a plurality of arm members mountedfor lifting movement on the truck and extending forwardly thereof inparallel spaced relation, a plurality of opposed clamp members mountedin the sides of said arm mem bers and extending inwardly into the spaceformed between each pair of arm members, a closed common fluid circuitcontaining a pressure producing fluid and contained within the fork armassembly interconnecting said clamp members, pressure producing means insaid fluid circuit associated with each arm member and connected to thepressure producing fluid including means overlying each arm memberadapted upon lifting movement thereof to contact the underside of a loadto be conveyed, engagement with said load causing the pressure producingmeans to be actuated downwardly relative to said arm memberstransmitting through the fluid a force which acuates simultaneously byway of the common fluid circuit and at a common fluid pressure the clampmeans into the space formed between the respective clamping arms toforcefully engage opposite sides of rows of a lowermost tier of the loadlocated in the spaces formed between the arm members.

5. A device as claimed in claim 4 wherein manually adjustable pistonmeans is provided for producing an initial pressure in the fluid priorto engagement of the pressure producing means with a load.

6. A device as claimed in claim 4 wherein said pres sure producing meansincludes piston means connected to the member overlying each arm member,and other piston means connected to the member overlying each arm memberand by means of the fluid in the system to the clamping members forrestoring the clamping members to initial non-clamping position uponlowering movement of the pressure producing means out of engagement witha load.

7. A device as claimed in claim 6 wherein manually adjustable pistonmeans is also provided for producing an initial pressure in the fluidprior to engagement of the pressure producing means with a load.

References Cited in the file of this patent UNITED STATES PATENTS2,685,976 Ulinski Aug. 10, 1954 2,983,397 Hirschboeck May 9, 1961FDREIGN PATENTS 1,087,077 France Aug. 18, 1954 1,088,119 France Sept. 1,1954

1. A DEVICE USABLE WITH LIFT TRUCKS AND THE LIKE FOR ENGAGING,TRANSPORTING AND DEPOSITING MATERIAL SUCH AS BRICKS, TILE, BLOCKS OR THELIKE, COMPRISING A PAIR OF FORK ARMS SUPPORTED FROM THE TRUCK ANDEXTENDING FORWARDLY THEREOF IN PARALLEL SPACED RELATION, A PLURALITY OFPAIRS OF OPPOSED RECIPROCABLE CLAMPING MEMBERS MOUNTED INSIDE THE FORKARMS AND EXTENDING OUTWARDLY THEREOF INTO THE SPACE FORMED THEREBETWEEN,A COMMON FLUID PRESSURE TRANSMITTING MEDIUM INTERCONNECTING ALL OF SAIDCLAMPING MEMBERS IN EACH FORK ARM, AND A FLUID PRESSURE PRODUCING MEANSMOUNTED INSIDE THE FORK ARMS FOR GENERATING FLUID PRESSURE IN THEPRESSURE TRANSMITTING MEDIUM UPON LIFTING MOVEMENT OF THE FORK ARMS TOSUPPORT A LOAD, SAID FLUID PRESSURE PRODUCING MEANS BEING THE SOLE MEANSASSOCIATED WITH THE DEVICE FOR GENERATING FLUID PRESSURE IN SAIDPRESSURE TRANSMISSION MEDIUM, SAID GENERATED FLUID PRESSURE TRANSMITTINGTHROUGH SAID COMMON FLUID PRESSURE TRANSMITTING MEDIUM FORCES CAUSINGALL OF SAID CLAMPING MEMBERS IN EACH FORK ARM TO BE ACTUATED TOWARD EACHOTHER INTO THE SPACE BETWEEN THE FORK ARMS.